The field of the present disclosure relates generally to turbine engines and, more specifically, to methods of determining a sensor probe location in a closed loop emissions control (CLEC) system.
At least some known gas turbine engines are used to generate electricity in power plants. Typically, the gas turbine engine includes a turbine compressor that compresses an air flow and a turbine combustor that combines the compressed air with fuel and ignites the mixture to generate combustion gases. As the combustion gases are expanded through a turbine, the turbine is rotated, and a turbine generator coupled via a shaft to the turbine is rotated to generate power. The turbine also generates exhaust gases that are channeled through an axial exhaust duct prior to being discharged through an exhaust stack. To comply with environmental particulate monitoring requirements, for example, at least some gas turbine engines include a CLEC system that continuously monitors the flow of gas emissions through the exhaust duct. More specifically, the CLEC system measures an amount of particulate in the exhaust flow exiting the gas turbine engine.
At least some known CLEC systems include one or more sensor probes (also referred to as “sample extraction probes”) that are positioned in the exhaust duct for sensing the amount of particulate in the exhaust flow. To ensure accurate measurements, the sensor probes are located within the exhaust duct in a recirculation zone at a “sweet spot” that represents a well-mixed exhaust flow. Known systems cannot be tuned to have higher sensitivity towards any one particular component of the emissions profile. Additionally, the sweet spot is generally located through a trial and error process until the sweet spot is identified. This may involve time-consuming field validation work during the commissioning of the CLEC system to validate the sweet spot against the continuous emissions monitoring system (CEMS) at the exhaust stack. The CLEC system may induce field variability. As such, the actual measurement variation is a function of variability in ambient conditions, unless the same vendor technology is used at the exhaust stack and at the CLEC system location to cancel out any ambient variation effect.